This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. At this time, all x-ray structures for holo and core RNAP are from the thermophiles T. thermophilus and T. aquaticus, neither of which appears to encode a DksA homolog recognizable from sequence analysis. We tested whether E. coli DksA would function on T. thermophilus or T. aquaticus RNAP. Unfortunately, E. coli DksA neither inhibited transcription nor reduced the half-lives of promoter complexes formed by these enzymes.Therefore, we concluded that it would not be prudent to attempt to get crystals for a heterologous complex containing E. coli DksA and T. thermophilus RNAP. Therefore, we have decided to use nuclear magnetic resonance (NMR) spectroscopy to define amino acid residues in E. coli DksA that are contacted by E. coli RNAP.